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Re: [libvirt] [PATCH] udev: fix crash in libudev logging



On 06/10/2013 05:05 PM, Guan Nan Ren wrote:
> I have been trying to fix this bug these days, but I failed to find a good way
> to bypass the warning you mentioned above caused by a gcc bug:
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28492
> 
> I can not find a better way than the casting in your code to compress the warning.
> other than this, there are some points needed to pay attention.
> 1, the log string output from udev ends with newline character which we could remove.

Yes that would be nice.

> 2, we can use debug mode for these logs.

Or we could use the message priority libudev gave us.

> 
> The following is the code with my code squashed in your casting code to fix this bug
> 
> diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c
> index 620cd58..dc989e9 100644
> --- a/src/node_device/node_device_udev.c
> +++ b/src/node_device/node_device_udev.c
> @@ -348,15 +348,32 @@ static int udevGenerateDeviceName(struct udev_device *device,
>  }
>  
>  
> -static void udevLogFunction(struct udev *udev ATTRIBUTE_UNUSED,
> -                            int priority ATTRIBUTE_UNUSED,
> -                            const char *file,
> -                            int line,
> -                            const char *fn,
> -                            const char *fmt,
> -                            va_list args)
> +typedef void (*udevLogFunctionPtr)(struct udev *udev,
> +                                   int priority,
> +                                   const char *file,
> +                                   int line,
> +                                   const char *fn,
> +                                   const char *format,
> +                                   va_list args);
> +
> +static void
> +ATTRIBUTE_FMT_PRINTF(6,0)
> +udevLogFunction(struct udev *udev ATTRIBUTE_UNUSED,
> +                int priority ATTRIBUTE_UNUSED,
> +                const char *file ATTRIBUTE_UNUSED,
> +                int line ATTRIBUTE_UNUSED,
> +                const char *fn ATTRIBUTE_UNUSED,

You're ignoring priority, file, line and fn. I think those might be useful.
I'll send another version.

> +                const char *fmt,
> +                va_list args)
>  {
> -    VIR_ERROR_INT(VIR_LOG_FROM_LIBRARY, file, line, fn, fmt, args);
> +    char *eol = NULL;
> +    char buffer[LINE_MAX];
> +    vsnprintf(buffer, sizeof(buffer), fmt, args);
> +
> +    if ((eol = strpbrk(buffer, "\n\r")))
> +        *(eol++) = 0;
> +
> +    VIR_DEBUG("%s", buffer);
>  }
>  

Jan


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